1. Field of the Invention
The present invention relates to a dust-proof reinforcing sheet material to be applied over and around a handling opening of a box, typically made of a paper board or corrugated board, the process for preparing the same and the process for the application thereof on the wall of the box. More particularly, the invention is directed to a composite web comprising a base sheet having a row of through-holes punched out to be arranged equi-distant apart, and a highly elastic and lighttransmissible film extending over the said through-holes.
2. Prior Art
A box made of corrugated paper widely used to contain goods therein for storage and transportation purposes is provided with access or handling openings at both side walls thereof for allowing four fingers of the handler to be inserted therethrough so that the handler may firmly grasp the side walls by hands. However, if the content in the box is one of the precision parts of an electronic machine, foodstuff or medicines, etc., there arises a risk that dusts or vermin, such as insects or rat, might get into the box through the openings. In order to exclude the invasion of dusts or vermin and to obviate deterioration of the goods or hygienic problems caused thereby, a small box made of corrugated paper without openings had to be used by now. However, the use of small container box leads to the need of a larger number of boxes for the package of a given volume of the content to be packed therein. This inevitably results in larger consumption of the material for the container boxes.
To solve the problems caused by the provision of through-opening, it has hitherto been proposed to use a reinforcing sheet having a center hole for receiving the fingers of the handler therethrough and an inwardly-projecting bag having the periphery adhering around the center hole in a dust-proof fashion. However, the container box provided with the inwardly-projecting dust-proof bag according to this prior-made proposal has disadvantages that dusts tend to accumulate in the bag to make the fingers of the handler dirty, that the projecting bag hinders the put-in and put-out operations of the content, and that the bag is apt to be broken by the finger nails of the handler or the edges or corner of the content resulting in serious contamination problem since the bag is made of a non-elastic material.
Another disadvantage of the prior-made proposal described above is that the reinforcing sheet having the center hole and the inwardly-projecting bag attached around the periphery of the center hole must be prepared through a cumbersome and laborconsuming manner and the thus prepared reinforcing sheet must be applied around each opening of the container box by hand, because no automatic and continuous process has been developed by now, resulting in increase in production cost.